In electricity generation using steam driven turbines, water is heated by a burner to create steam which drives a turbine to create electricity. Also in other industrial processes water is needed for cooling. In order to minimize the amount of clean water necessary for this process, the steam must be converted back into water, by removing heat, so that the water can be reused in the process. In air conditioning systems for large buildings, air inside the building is forced passed coils containing a cooled refrigerant gas thereby transferring heat from inside the building into the refrigerant gas. The warmed refrigerant is then piped outside the building where the excess heat must be removed from the refrigerant so that the refrigerant gas can be re-cooled and the cooling process continued.
In both of the foregoing processes, and numerous other processes that require the step of dissipating excess heat, cooling towers have been employed. In wet type cooling towers, water is pumped passed a condenser coil containing the heated steam, refrigerant, or other heated liquid or gas, thereby transferring heat into the water. The water is then pumped to the top of the heat exchangers and sprayed over a cooling tower media comprised of thin sheets of material or splash bars. As the water flows down the cooling tower media, ambient air is forced passed the heated water and heat is transmitted from the water to the air by both sensible and evaporative heat transfer. The air is then forced out of the cooling tower and dissipated into the surrounding air.
Cooling towers are highly efficient and cost effective means of dissipating this excess heat and thus are widely used for this purpose. A recognized drawback to cooling towers, however, is that under certain atmospheric conditions a plume can be created by moisture from the heated water source evaporating into the air stream being carried out of the cooling tower. Where the cooling tower is very large, as in the case of power plants, the plume can cause low lying fog in the vicinity of the cooling tower. The plume can also cause icing on roads in the vicinity of the cooling tower where colder temperatures cause the moisture in the plume to freeze. Efforts have therefore been made to limit or eliminate the plume caused by cooling towers.
One common way to limit plume is the introduction of ambient air. For example, plume abated cooling towers are employed where ambient air, in addition to being brought in at the bottom of the tower and forced upwards through a fill pack as hot water is sprayed down on the fill pack, is brought into the cooling tower through isolated heat conductive passageways above the hot water spray heads. These passageways which are made from a heat conductive material such as aluminum, steel, copper, etc., allow the ambient air to absorb some of the heat without moisture being evaporated into the air. Also, above the cooling fill, the wet laden heated air and the dry heated air are mixed thereby reducing the plume.
Another cooling tower orientation employs a plume abatement system in which the hot water is partially cooled before being provided into the cooling tower. The partial cooling of the hot water is performed using a separate heat exchanger operating with a separate cooling medium such as air or water. The separate heat exchanger reduces the efficiency of the cooling tower and thus should only be employed when atmospheric conditions exist in which a plume would be created by the cooling tower.
Another example of a system designed to reduce plume in a wet type cooling tower entails pumping hot water through a dry air cooling section where air is forced across heat exchange fins connected to the flow. The water, which has been partially cooled, is then sprayed over a fill pack positioned below the dry air cooling section and air is forced through the fill pack to further cool the water. The wet air is then forced upwards within the tower and mixed with the heated dry air from the dry cooling process and forced out the top of the tower.
While the foregoing systems provide heat exchange for industrial processes in combination with solutions for addressing plume abatement, these systems or solutions oftentimes require the construction of a complex, and oftentimes costly, wet and dry air heat transfer mechanisms. This cost is partly due to each respective heat transfer mechanism, wet and dry, requiring use of separate vertical fan systems to provide air flow through their respective wet and dry sections. For example, during operation of such systems, and individual fan system is required to provide an air stream through the dry section and a second, separate fan system is required to provide an air stream through the wet section. The employment of the separate wet and dry fan systems add additional construction cost during construction. Also, the fan apparatus for the dry sections are typically oriented in a vertical position, requires the tower height to be significantly larger which is often times not desired or allowed. Moreover, each the individual fan systems require maintenance during the life cycle of the cooling tower systems, adding to the cost of operation of such systems.
Another drawback is the foregoing systems and design is the above-discussed fan assemblies are vertical in orientation as previously mentioned. This vertical orientation while may not be a drawback per se, it requires that the fans be a limited size and therefore additional fan assemblies may be required. This vertical orientation requires the towers to be larger in height and space as previously discussed increasing the vertical size of said cooling towers, potentially limiting the locations where the tower may be employed.
The foregoing shows that there is a need for a cost efficient cooling tower that allows for plume abatement as needed, in an efficient, economical manner. Moreover there is a need for a cost effective cooling tower system that utilizes an efficient plume abatement system would therefore be desirable.